Radio systems are intended to handle a wide range of signal strengths. In a digital radio system the analog to digital converter (“ADC”) places a constraint on the range of signals that may be handled. The range of signals that can be reliably transmitted in a device is described as the dynamic range. Digitizing electronics are often carefully designed so the dynamic range encompasses the range of information signals utilized by the device. Thus an ADC trying to record, with acceptable resolution, light pulses from low magnitude signals such as minimum ionizing tracks and from higher magnitude signals such as energetic showers in a calorimeter, will necessarily need a large information range (usually given as a word length, e.g. 10 or more bits). The dynamic range is sometimes expressed as the ratio between the highest and lowest signal and may be measured in decibels (i.e. the logarithmic expression of this ratio).
In prior art methods, the effective range of an ADC may be extended by using a non-linear response. This approach extends the dynamic range, preserving all relevant information; however, some processing is required so that the information is translated back to a linear scale. For a non-linear response, the error given by the least count (i.e. the smallest step by which digitized signals can be different) does not translate into a constant absolute error, resulting in different degrees of resolution dependent upon signal strength.
A prior art digital radio system uses two gain stages to extend the dynamic range of the ADC. This prior art system takes samples only during hopping where a hop's worth of samples are accumulated for each stream and a choice of which stream to use is then determined at the end of a hop. In this prior art system the samples are taken at different times for each stage. Consequently, the streams cannot be combined.
Other prior art approaches to extend the dynamic range of an ADC employ automatic gain control (AGC) loops. Prior art radios employing this method are designed to implement a plurality of communication techniques each of which imposes unique requirements on the AGC used. In the prior art, attempts have been made to implement AGC algorithms in software so that each waveform might have a unique algorithm customized to its particular needs. However, the software generally introduces delays into the control loop making it nearly impossible to implement stable and effective gain control loops.
In view of the present need and the deficiencies of the prior art, it is an object of an embodiment of the present invention to provide a novel method and system to extend the dynamic range of a digital system without introducing a control loop and to allow a quasi, non-causal and stable gain control algorithm to be implemented in software.
It is also an object of an embodiment of the present invention to provide a radio receiver to handle a range of signals that is outside the capabilities of current analog to digital converters.
It is another object of an embodiment of the present invention to provide a radio frequency receiver for receiving a plurality of signal strengths wherein said radio receiver contains a plurality of gain streams, an ADC, a controller and a digital signal processor. Furthermore, said gain streams contain an amplifier applying a different incremental gain to the communication signal.
It is yet another object of an embodiment of the present invention to provide an improvement of an apparatus for converting an analog signal to a digital signal where the apparatus includes a quantifier with a fixed dynamic range, a DSP and at least two fixed gain amplifying parallel branches. Wherein, each said fixed gain amplifying branches amplify the analog signal. The improvement comprises using gain amplifiers that have different gains in the parallel branches.
It is still another object of an embodiment of the present invention to provide a method to extend the dynamic range of a radio receiver without a gain control loop. The method includes the steps of obtaining a communication signal, amplifying the signal at different gains and converting the signal to digital data.
It is still yet another object of an embodiment of the present invention to provide a novel signal processing apparatus for recovering information from an analog input signal and producing a digital output signal representative of said information. The apparatus including comprising plural parallel circuits each adapted to receive said analog input signal and produce therefrom a quantized signal which is amplified by an amount different than the other said parallel circuits. The apparatus also including a logic circuit for receiving the quantized signals from the parallel circuits and recovering said information from the quantized signals to thereby produce a digital output signal representative of said information.
It is an additional object of an embodiment of the present invention to provide a novel improvement to a signal processing apparatus for recovering information from an analog input signal and producing a digital output signal representative of said information including a signal processing circuit including a quantizer with a fixed dynamic range. The improvement including plural parallel circuits replacing said signal processing circuit wherein said plural parallel circuits are each-adapted to receive said analog input signal and produce therefrom a quantized signal which is amplified by an amount different than the other said parallel circuits. The improve signal processing apparatus also including a logic circuit for receiving the quantized signals from the parallel circuits and recovering said information from the quantized signals to thereby produce a digital output signal representative of said information.
It is still an additional object of an embodiment of the present invention to provide a novel improvement for a signal processing apparatus for recovering information from an analog input signal and producing a digital output signal representative of said information, wherein said apparatus comprises a signal processing circuit including a quantizer with a fixed dynamic range and an AGC loop. The improved signal processing apparatus including plural parallel circuits replacing said signal processing circuit wherein said plural parallel circuits are each adapted to receive said analog input signal and produce therefrom a quantized signal which is amplified by an amount different than the other said parallel circuits. The improved signal processing apparatus also including a logic circuit for receiving the quantized signals from the parallel circuits and recovering said information from the quantized signals to thereby produce a digital output signal representative of said information.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.